In battle today noticed NPCs going negative on engines when getting shot from behind. During the allocation period the NPC even repaired some of the negative engines going from -13 to -11.
Thanks for the heads-up, its a known bug -- once the ship capture feature is implemented -- when a ship has 0 crew it would be captured by marines, and become Auto AI controlled to leave the area. The engines at that point would remain 0, and not go negative.